1. Field of the Invention
The present invention relates to a torsion damper, especially a disc type friction clutch for an automotive vehicle, of the kind comprising a lining support plate and a hub which are movable angularly with respect to each other within the limits of a predetermined angular displacement, the support plate and the hub being coupled together by two torsion damping devices arranged to act successively, one of which (referred to as the first device or pre-damper), is weaker than the other (referred to as the second device or main damper) which comprises a damper plate mounted on the hub with a clearance permitting the said angular displacement, two rings, referred to as guide rings, fixed with respect to each other and disposed on either side axially of the damper plate, and a plurality of resilient angular displacement means interposed circumferentially between the damper plate and the rings, and further comprising associated friction means.
2. Description of the Prior Art
French Patent Application No. 2 386 729 describes a damper with a predamper comprising a resilient means disposed within the zone of co-operation provided between the hub and the damper plate of the main damper. A bush mounted on the hub, and rotatable with one of the guide rings, ensures only that the guide rings are centred with respect to the hub.
The Certificate of Addition No. 2 570 147 to French Patent Application No. 2 551 813 discloses a pre-damper comprising a damper plate, two guide rings disposed axially on either side of the damper plate, and resilient means interposed circumferentially between the damper plate and the rings, the said plate being rotatable with the hub so that the guide rings are rotatable with the damper plate of the main damper.
Coupling between the pre-damper and the main damper is obtained by means of cylindrical members projecting from one guide ring of the pre-damper and engaged in recesses in the damper plate of the main damper. These members ensure positioning of the guide rings of the pre-damper with respect to the damper plate of the damper, but they do not ensure that the said damper plate is centred with respect to the hub.
In European Patent Application No. 0 209 316, the pre-damper includes wedging means, and a bearing is provided to centre the damper plate on the hub.
For this purpose axial elements for centring the damper plate with respect to the hub are provided, projecting axially between the damper plate and a face plate fixed with respect to the bearing. These elements are fixed with respect to the face plate.
During operation in all these cases, radial forces will always develop within the damper, so that imbalance phenomena, which contribute to the incidence of vibration, cause an increase in wear in the damper components. In addition, these radial forces do not lead to good friction control within the pre-damper, especially in connection with the bush.
An object of the present invention is to reduce these disadvantages and therefore to create an arrangement allowing the radial forces developing within the pre-damper, and wear in the damper, to be reduced while allowing good friction control in the pre-damper and obtaining other advantages.